Wireless communication systems require identifiers to identify mobile devices over networks such as GSM networks, 3G networks, 4G networks and the like. A SIM (subscriber identity module) is conventionally used to store the indentification number, typically referred to as an IMSI.
A SIM may be provided in the form of a card, a SIM card, or alternatively in the form of a chip simply mounted in wireless apparatus by any other way, for example by being soldered to a circuit board.
When roaming, automatic rules are used to select a network. The network provider provides a list of preferred networks and the SIM automatically selects a network from the available networks in any location according to the preference list.
More recently, SIMS with multiple IMS1's have been marketed, in particular for use by international travelers. Such a SIM includes two IMSIs, typically local in two different countries, for example the US and the UK. The user may select which IMSI is required by typing in a different password on power up for each IMSI. In this way, the user may select a suitable IMSI depending on the user's location.
WO2011/041913 describes an extension of this idea to a system for remote monitoring of a meter or other remote asset; a SIM is provided with multiple IMSIs.
However, the use of multiple identities causes issues in a number areas, including selection of the correct IMSI, which may be less easy than it at first appears. For example, many networks restrict which services are available to roaming SIMs so simply finding an apparently valid network may deliver a voice capability but not an adequate data capacity. Further, where a replacement IMSI is downloaded over air there is a risk of the SIM ending up with no valid IMSIs which means that there is no further connectivity, and hence no further possibility of communicating with the device which then loses all functionality.
The present application is concerned with addressing some of these difficulties.